Philipp Rudolph Castelhun (1838-1864) was a German-American watchmaker in St. Louis, Missouri.  He served in the Union Army and died of pulmonary tuberculosis in 1864.  This artwork was commissioned by his family in 1866 at Cramer & Gross, 333 S. 4th Street, St. Louis, and it was based on a daguerreotype that was most likely shot in 1856.  The original photo had also included Rudolph's older sister Adelheid Castelhun Weidenbach (1832-1900), but she wasn't included in the final artwork since it was meant to honor and remember the deceased 26-year-old.  The oldest brother, Friedrich Karl Castelhun, named his second son Rudolph Castelhun, but he too passed away much too soon.